U.S. patent number 6,834,547 [Application Number 10/440,934] was granted by the patent office on 2004-12-28 for humidity sensor and fabrication method thereof.
This patent grant is currently assigned to Nanya Technology Corporation. Invention is credited to Chih-Kun Chen, Yao-Hsiung Kung, Chung-Min Lin, Hsin-Chuan Tsai.
United States Patent |
6,834,547 |
Chen , et al. |
December 28, 2004 |
Humidity sensor and fabrication method thereof
Abstract
A humidity sensor and fabrication method thereof. In the
humidity sensor of the present invention, two comb-type electrodes
with a plurality of teeth are disposed on a semiconductor
substrate. A SiO.sub.2 sensing film is disposed between the teeth
of the two comb-type electrodes on the substrate. A predetermined
voltage is applied between the two comb-type electrodes, a leakage
current between the two electrodes is detected, and the humidity in
the environment is measured according thereto.
Inventors: |
Chen; Chih-Kun (Taoyuan,
TW), Kung; Yao-Hsiung (Taoyuan, TW), Lin;
Chung-Min (Taipei, TW), Tsai; Hsin-Chuan (Taipei,
TW) |
Assignee: |
Nanya Technology Corporation
(Taoyuan, TW)
|
Family
ID: |
31974899 |
Appl.
No.: |
10/440,934 |
Filed: |
May 19, 2003 |
Foreign Application Priority Data
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Aug 28, 2002 [TW] |
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91119512 A |
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Current U.S.
Class: |
73/335.02;
73/29.05 |
Current CPC
Class: |
G01N
27/121 (20130101) |
Current International
Class: |
G01N
27/12 (20060101); G01N 001/00 (); G01N
019/00 () |
Field of
Search: |
;73/29.01,335.02,335.03,335.04,335.05,29.05 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Larkin; Daniel S.
Attorney, Agent or Firm: Quintero Law Office
Claims
What is claimed is:
1. A humidity sensor, comprising: a substrate; two comb-type
electrodes disposed on the substrate, each having a plurality of
teeth spaced apart from adjacent teeth by 0.175 micrometers; and a
SiO.sub.2 sensing film disposed between the teeth of the two
comb-type electrodes on the substrate, wherein a processing unit
applies a predetermined voltage between the two comb-type
electrodes, detects a leakage current therebetween, and determines
the humidity in the environment according thereto.
2. The humidity sensor as claimed in claim 1, wherein the two
comb-type electrodes are made of metal.
3. The humidity sensor as claimed in claim 1, wherein the two
comb-type electrodes are made of polysilicon.
4. The humidity sensor as claimed in claim 1, wherein each
comb-type electrode has a pad thereon.
5. The humidity sensor as claimed in claim 1, wherein the opposing
teeth of the two comb-type electrodes alternate.
6. A method of fabricating a humidity sensor, comprising: providing
a substrate; forming a SiO.sub.2 layer on the substrate as a
sensing film; forming two comb-type trenches each with a plurality
of teeth on the SiO.sub.2 layer; and filling a conductive material
into the two comb-type trenches to form two comb-type
electrodes.
7. The method as claimed in claim 6, wherein the conductive
material is metallic.
8. The method as claimed in claim 6, wherein the conductive
material is polysilicon.
9. The method as claimed in claim 6, further comprising a step of
forming two pads on the comb-type electrodes respectively, wherein
the SiO.sub.2 layer is formed by chemical vapor deposition with
TEOS and O.sub.3.
10. A method for detecting humidity in a predetermined environment;
comprising: providing a humidity sensor in the predetermined
environment for a predetermined time, wherein the humidity sensor
has a substrate, two comb-type electrodes deposed on the substrate,
each having a plurality of teeth, and a SiO.sub.2 sensing film
between the teeth of the two comb-type electrodes on the substrate;
applying a predetermined voltage difference between the two
comb-type electrodes, wherein the predetermined voltage difference
is about 1.8 V; detecting a leakage current between the two
comb-type electrodes; and determining the humidity in the
predetermined environment according to the leakage current.
11. The method as claimed in claim 10, wherein the humidity in the
predetermined environment is determined by a relational table
between leakage current and humidity.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sensor, and in particular to a
humidity sensor, its detection method, and fabrication thereof.
2. Description of the Related Art
Conventionally, humidity sensors detect humidity in an environment
and are generally used in air conditioning systems, dehumidifiers,
dryers, and the like. Such wide use requires the humidity sensors
to provide dependable operation.
Consequently, the humidity sensors can be mass produced at low cost
if utilizing semiconductor process together with a simple structure
and process, and lower material consumption.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a humidity
sensor with a simple structure, its method of detection, and
fabrication method thereof.
Another object of the invention is to provide a method for
detecting the humidity in the environment.
According to the above mentioned objects, the present invention
provides a humidity sensor. In the humidity sensor of the present
invention, two comb-type electrodes with a plurality of teeth are
disposed on a semiconductor substrate. A SiO.sub.2 sensing film is
disposed between the teeth of the two comb-type electrodes on the
substrate. A predetermined voltage is applied between the two
comb-type electrodes, leakage current between the two electrodes is
detected, and the humidity in the environment is measured according
thereto.
In the fabrication method of the present invention, a SiO.sub.2
layer is formed on a semiconductor substrate as a sensing film. Two
comb-type trenches, each with a plurality of teeth, are formed on
the SiO.sub.2 layer and a conductive material is filled into the
two comb-type trenches to form two comb-type electrodes.
The present invention also provides a method for detecting humidity
in a predetermined environment. In the detection method, a humidity
sensor is provided in the predetermined environment for a
predetermined time, wherein the humidity sensor has a substrate,
two comb-type electrodes deposed on the substrate, each having a
plurality of teeth, and a SiO.sub.2 sensing film between the teeth
of the two comb-type electrodes on the substrate. A predetermined
voltage difference is then applied between the two comb-type
electrodes, and a leakage current between the two comb-type
electrodes is determined. Finally, the humidity in the
predetermined environment is determined according to the leakage
current.
A detailed description is given in the following embodiments with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention can be more fully understood by reading the
subsequent detailed description and examples with references made
to the accompanying drawings, wherein:
FIG. 1 illustrates the sensing principle of a humidity sensor
according to the present invention;
FIG. 2 shows the relationship between time and leakage current when
a SiO.sub.2 film is exposed to the environment;
FIG. 3 shows the relationship between time and leakage current when
a SiO.sub.2 film is exposed in a box;
FIGS. 4a.about.4d are cross-sections of the fabrication method
according to the present invention;
FIGS. 5a.about.5d are plane views of FIGS. 4a.about.4d;
FIG. 6 is a diagram for the detection method of the present
invention; and
FIG. 7 shows the relationship between the leakage current and
humidity when spacing between teeth of the comb-type electrodes is
varied.
DETAILED DESCRIPTION OF THE INVENTION
The present invention senses the humidity in an environment by
SiO.sub.2 sensing film and the sensing principle thereof is
Illustrated and referenced in FIG. 1 and FIG. 2. FIG. 1 is a
diagram of the humidity sensor according to the present invention.
FIG. 2 shows the relationship between time and leakage current when
a SiO.sub.2 film is exposed to the environment. As shown in FIG. 1,
when a SiO.sub.2 film 10 is disposed in a detecting environment,
the surface layer 10A of the SiO.sub.2 film absorbs the humidity.
Consequently, the charge density In the surface layer 10A of the
SiO.sub.2 film changes the surface layer 10A to a conductive layer
from an isolation layer. Thus, a leakage current can be measured by
applying a voltage difference between the electrodes 11A and 11B.
As shown In FIG. 2, the surface layer 10A has absorbed humidity and
is saturated after time Ts, and the leakage current between the
electrodes trends to be constant. Thus, the humidity concentration
in the detected environment is obtained according to the leakage
current between the electrodes 11A and 11B after time Tp.
FIG. 3 shows the relationship between time and leakage current when
a SiO.sub.2 film is exposed to the atmosphere in a box,
respectively. In FIG. 3, the curve C.sub.1 shows the relationship
between time and leakage current when a SiO.sub.2 film is exposed
in a box, and the curve C.sub.2 shows the relationship between time
and leakage current when a SiO.sub.2 film is exposed to the
atmosphere. Thus, the leakage current between the electrodes 11A
and 11B in atmosphere is larger than that in the box when applying
a voltage difference between the two electrodes.
FIGS. 4a.about.4d are cross-sections of the fabrication method
according to the present invention, and FIGS. 5a.about.5d are plane
views of FIGS. 4a.about.4d.
As shown in FIGS. 4a and 5a, a semiconductor substrate 20 is
provided. As shown in FIGS. 4b and 5b, a SiO.sub.2 sensing film 22
is formed on the semiconductor substrate 20 by chemical vapor
deposition (CVD) using tetraethyl orthosilicate (TEOS) and O.sub.3
as process gases. Alternately, the SiO.sub.2 sensing film 22 may be
formed on the semiconductor substrate 20 by thermal oxidation.
As shown in FIGS. 4c and 5c, two comb-type trenches 14a and 14b are
formed in the SiO.sub.2 sensing film 22 by photolithography and
etching, wherein each comb-type trench has a plurality of teeth
with each tooth a predetermined distance, for example 0.175
micrometers, from adjacent teeth.
In FIGS. 4d and 5d, a conductive material 16 is filled into the two
comb-type trenches 14a and 14b to form two comb-type electrodes 16a
and 16b. In the present invention, the two electrodes 16a and 16b
are made of conductive material, such as polysilicon material or
metallic material, for example Au, Cu, Ag, Al, W and the like. The
conductive material is filled into the trenches 14a and 14b and on
the whole surface of the semiconductor substrate 20 by deposition
or sputtering. The conductive material outside the trenches 14a and
14b is then removed by chemical mechanical polishing. Each of the
two comb-type electrodes 16a and 16b has a pad (17a and 17b)
coupled to a voltage source, and a plurality of teeth. Each tooth
of the comb-type electrodes 16a and 16b is a distance, such as
0.175 micrometers, from the adjacent teeth, such that the opposing
teeth of the comb-type electrodes 16a end 16b alternate.
FIG. 6 shows the humidity sensor 200 of the present invention, in
which two comb-type electrodes 16a and 16b are formed on a
semiconductor substrate 20, each having a pad (17a and 17b) coupled
to a voltage source and a plurality of teeth. Each tooth of the
comb-type electrodes 16a and 16b is a distance, such as 0.175
micrometers, from the adjacent teeth, such that the opposing teeth
of the comb-type electrodes 16a and 16b alternate. A SiO.sub.2
sensing film is formed between the two electrodes 16a and 16b and
on the surface of the semiconductor substrate 20. When an
appropriate voltage difference is applied between the two comb-type
electrodes 16a and 16b, a leakage current therebetween is
obtained.
The present invention also provides a method for detecting humidity
in a detecting environment. In the detection method, a humidity
sensor 200 as shown in FIG. 6 is provided, with a relational table
between the leakage current and corresponding humidity levels
previously established. The relational table is established by
measuring leakage current between the comb-type electrodes under
varying humidity levels.
The humidity sensor 200 is then disposed in a detecting environment
for a predetermined time. A processing unit (not shown) then
applies a predetermined voltage difference, for example 1.8V,
between the two comb-type electrodes 16a and 16b, and detects the
leakage current therebetween.
Finally, the humidity of the detecting environment is obtained
according to the detected leakage current and the relational
table.
Thus, the present invention can detect the humidity in a detecting
environment.
In addition, FIG. 7 shows the relationship between humidity and
leakage current between the comb-type electrodes with varying teeth
spacing. In FIG. 7, the curve C.sub.3 shows the relationship
between humidity and leakage current when the space between the
teeth of the comb-type electrode is 0.175 micrometers, and the
curve C.sub.4 shows the relationship between humidity and leakage
current when the space between the teeth of the comb-type electrode
is less than 0.1 micrometer. As shown in FIG. 7, the humidity
sensor has increased sensitivity as the space between teeth of the
comb-type electrodes decreases. Therefore, as semiconductor
technology advances, the space between teeth of the comb-type
electrodes decreases, enhancing sensitivity of the humidity
sensor.
Furthermore, the humidity absorbed into the SiO.sub.2 sensing film
can be removed by heating for a time, such that the humidity sensor
can be reused to detect humidity in another environment. The
humidity sensor can also be coupled to peripheral circuits and
formed on a semiconductor chip for applications, such as air
conditioning systems, dehumidifiers, dryers, and the like.
While the invention has been described by way of example and in
terms of the preferred embodiments, it is to be understood that the
invention is not limited to the disclosed embodiments. To the
contrary, it is intended to cover various modifications and similar
arrangements (as would be apparent to those skilled in the art).
Therefore, the scope of the appended claims should be accorded the
broadest interpretation so as to encompass all such modifications
and similar arrangements.
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